This invention relates to railroad grade crossings, and in particular to railroad grade crossings using both concrete and rubber elements.
In high traffic areas, such as downtown city streets, concrete is the preferred material for railroad grade crossings due to its resistance to wear. In order to reduce the cost and disruption resulting from maintenance, it has become common in this type of environment to provide precast concrete pads which serve both as the crossing and support the rails. The use of these pads eliminates the need for ties and ballast which require periodic maintenance. In order to facilitate the installation and replacement of the rails, the portion of the crossing between the rails is not an integral part of the pads but comprises removable concrete gauge panels. Crossing pads of this type are disclosed in Harmon, U.S. Pat. No. 3,317,137, and in O'Brien, et al., U.S. Pat. No. 4,641,779.
However, the prior art concrete pad grade crossing systems have several shortcomings. Because the concrete gauge panels extend one-half of the distance between the rails they are quite heavy and require the use of a crane to install and remove them. In addition, the prior art concrete gauge panels are attached to the concrete pad by placing bolts through counterbores in the panels and into engagement with threaded anchors embedded in the pad. Aligning the holes in the gauge panels with the anchors in order to start the bolts is difficult, and the process of starting and tightening a large number of bolts is very labor intensive. In addition, all of these bolts need to be loosened and removed to remove the gauge panels whenever maintenance is required.
While concrete crossing elements wear well there are advantages to rubber crossing elements, at least adjacent to the rails. Due to slight irregularities in the rail gauge, concrete gauge panels need to be shimmed in order to provide a tight fit against the rails. In addition, concrete panels will not seal against the rails as well as rubber panels and water will get between the panels and the rails which can weaken the foundation support and can cause damage when it freezes. Rubber panels also provide a smoother transition between the rail and grade crossing for vehicular traffic and are less likely to chip on the upper corners adjacent to the rails.
Composite concrete/rubber grade crossings are known in the prior art. However, these systems are all of the type where the rails are supported by ties and the concrete panels only serve as crossing elements not rail supporting pads. In Davis, U.S. Pat. No. 5,181,657, rubber crossing panels are placed on each side of the rails to provide a smooth transition and seal between the rails and the concrete panels that extend across the remainder of the crossing. With this system the concrete panels hold the rubber panels against the rails and on the ties. Thus, Davis, et al. does not address the problems associated with the prior art integral concrete pad crossing systems. Martin, U.S. Pat. No. 4,899,933, provides rubber seals between the rails and the concrete panels that make up the majority of the crossing. These seals are small and are held in place merely by friction. Thus, these seals do not really serve as a part of the crossing. Martin also does not address the problems associated with the prior art integral concrete pad crossing systems.
The subject invention solves the problems associated with the prior art integral concrete pad grade crossing systems by providing an integral rigid grade crossing pad having a pair of cavities defined in it to receive the rails. Each cavity has a planar bottom which supports the bottom flange of a rail, and a first side wall that conformingly contacts the field side of the rail. The rails are located in the respective cavities with their field side walls in contact with the cavity side walls and are secured to the pad with a rail anchor system. Preferably, the rails are wrapped in an electrically non-conductive elastomeric boot to electrically insulate and cushion them with respect to the pad. In a preferred embodiment of the invention the rail anchor system includes a clip having a first portion that partially overlies the rail flange and a second portion that contacts the bottom of the cavity. A bolt extends through a hole in the clip into threaded engagement with an insert embedded in the pad. Thus, by tightening the bolt the clip is clamped against the rail flange and the bottom of the cavity.
The remainder of each cavity is filled with an elastomeric insert which has the same depth as the cavity. One side of the insert conforms to the gauge side of the rail and the other side conforms to the inner side wall of the cavity. A notch located on the upper corner of the insert adjacent to the rail accommodates the flanges of the rail car wheels passing over the rails. The insert is releasably secured to the pad by an insert anchor system.
In a preferred embodiment of the invention the insert anchor system includes bulbous gripping heads that are attached to threaded anchors imbedded in the pad. The inserts contain aligned openings that conform to the shape of the gripping heads. Thus, the inserts can easily be secured to the pad simply by placing them in the cavity and urging them downwardly so that the gripping heads become frictionally engaged in their respective openings in the inserts. The inserts can be removed merely by pulling them away from the pad to disengage the gripping heads from the openings and then lifting them out of the cavities.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.